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go kart

rod burner
are you sure it is chrome molly ?
i have been around karts since 1959 and 4130 frames are rare there are some but very few (cost)
probably won't matter though 1016 and 4130 have been put together before just get the right rod/i usually pre heat and post heat any molly if o/a or heliarc( that dates me )just to make me comfy/ on most of the kart frames i use 309 if i don't know/ i know there will be some questions on the forum about this prosess but it has worked for me but listen to the good guys out ther that have more smarts than me
good luck pat from tx

I dont think cro-moly tubing is that hard to weld, I took the lincoln electric basic motorsports class 2 years ago, and the end of that class is a 4130 weld test. Basically weld a "T" and then weld a threaded bung on one end and its tested in a hydraulic jack type thing to test its tensile strength. Passing was if it held to aerospace standards, Im not sure what the exact numbers were, I have them in my welding folders, but anyways I passed, I just TIG welded using 309 stainless steel filler. I thought welding fell somewhere in between mild steel and stainless. You had to limit the heat input as to not weaken the 4130, but enough to have good solid penetration.

I still wouldnt recommend welding a kids go kart, just because if you dont have much experience in welding that material or that type of project, and then something happens, thats all on you. When it comes to welding something that has to do with someones safety, I stick to doing it for myself first, Id rather get myself hurt before someone else, especially a child.

I dont think cro-moly tubing is that hard to weld, I took the lincoln electric basic motorsports class 2 years ago, and the end of that class is a 4130 weld test. Basically weld a "T" and then weld a threaded bung on one end and its tested in a hydraulic jack type thing to test its tensile strength. Passing was if it held to aerospace standards, Im not sure what the exact numbers were, I have them in my welding folders, but anyways I passed, I just TIG welded using 309 stainless steel filler. I thought welding fell somewhere in between mild steel and stainless. You had to limit the heat input as to not weaken the 4130, but enough to have good solid penetration.

I still wouldnt recommend welding a kids go kart, just because if you dont have much experience in welding that material or that type of project, and then something happens, thats all on you. When it comes to welding something that has to do with someones safety, I stick to doing it for myself first, Id rather get myself hurt before someone else, especially a child.

Hate to tell you but that lincoln test is pretty useless. Tensile strength is not where welding induced failures are common, its usually a fatigue issue. I also have to question the technical tips given by a company that makes no legal standards and has no responsibility in the areas where their "process" will be used. I.E. Lincoln, Miller, or Esab have no right to make a recomendation for an application that is watched over by another engineering group ( NHRA, FAA, CAA etc. )

Hate to tell you but that lincoln test is pretty useless. Tensile strength is not where welding induced failures are common, its usually a fatigue issue. I also have to question the technical tips given by a company that makes no legal standards and has no responsibility in the areas where their "process" will be used. I.E. Lincoln, Miller, or Esab have no right to make a recomendation for an application that is watched over by another engineering group ( NHRA, FAA, CAA etc. )

I know this, I dont use the test as a basis to say Im a certified welder in cro-moly tubing. I include it in my resume along with all classes and jobs I have done to show that I have experience TIG welding, but other than that I know it has no real purpose. Considering that as far as I know there isnt a clear cut certification for TIG welding processes because there is so many different possibilities and different factors possible. Lincoln Electric didnt really falsely claim that by passing their test you are legitimately certified, they even state that its just a test to show that your weld withstands more tensile stress than the base metal. If you take the advanced motorsports class there you actually have the option to do a certified test that gets mailed out to some aerospace association (dont know exactlly what one), and they do the testing and certification.
I also want to say I dont think these classes are a waste or just another way to gain customers. I spent a week, 8 hours a day every day studying metallurgy, processes, and most of all welding, everything from stainless, to aluminum, mild steel, and cro-moly. The advanced class you get to do titanium, magnesium, more stainless, cro-moly, and inconel. And theres no limit, theres huge canisters filled with shrink wrapped and sealed metal coupons and tubing, all sizes and thicknesses, and you just keep grabbing handfuls for hours. You meet professional fabricators from the motorsports industry too, sometimes they even watch you weld, work with you, etc. I dont know about any of you guys, but no trade school around me offers that.

I know this, I dont use the test as a basis to say Im a certified welder in cro-moly tubing. I include it in my resume along with all classes and jobs I have done to show that I have experience TIG welding, but other than that I know it has no real purpose. Considering that as far as I know there isnt a clear cut certification for TIG welding processes because there is so many different possibilities and different factors possible. Lincoln Electric didnt really falsely claim that by passing their test you are legitimately certified, they even state that its just a test to show that your weld withstands more tensile stress than the base metal. If you take the advanced motorsports class there you actually have the option to do a certified test that gets mailed out to some aerospace association (dont know exactlly what one), and they do the testing and certification.
I also want to say I dont think these classes are a waste or just another way to gain customers. I spent a week, 8 hours a day every day studying metallurgy, processes, and most of all welding, everything from stainless, to aluminum, mild steel, and cro-moly. The advanced class you get to do titanium, magnesium, more stainless, cro-moly, and inconel. And theres no limit, theres huge canisters filled with shrink wrapped and sealed metal coupons and tubing, all sizes and thicknesses, and you just keep grabbing handfuls for hours. You meet professional fabricators from the motorsports industry too, sometimes they even watch you weld, work with you, etc. I dont know about any of you guys, but no trade school around me offers that.

Yep I know the test your talking about. The cluster on a plate so to speak. It dates from the 1940's and is purely a test of opperator skill, ive done it myself. My gripe with Lincoln etc. is not with certifying a "weldor" but pushing a "process" to people as being "gospel". I have seen many people come from classes like that, with the recomendations from the welder company, and try building an aircraft part. Over and over again I have to explain to them that what Lincoln, Miller or any other machine company says, is not relevant when a regulatory body has jurisdiction ( the FAA in this case ). I.E. Lincoln rep Buddy McBud can say till he is blue in the face that you dont need to say....post heat a particular weldment on an airframe, If the FAA says you do....guess what? Now again, my issue is limited to aviation as thats where Im involved with it. Racing and such is a whole different story.

No heat treatment or preheating is required because it is so thin. I'd tig it with ER70s, it will flex a little more than ER80. The most important thing is not to get it to hot. If it turns black it is ruined. Go buy some cromo tubing at a steel shop, my guess is it is 3/4" and probably .065 wall. It should not cost more than $2 a foot. A couple practice welds and you should be fine. Cromo tubing welds very similar to DOM tubing or cold rolled steel.

While I don't know the percentages in 4130. P11 & P22 pipe have 1 to 2 1/2% respectively I believe, and require 400 preheat, 750 interpass and postweld heat treatments. We weld them with ER80S-B2L or ER90S-B2L Tig wire.

I have a bicycle tube set made of 4130 Chrome-Moly but it is in several pieces - this is how it left the factory. It is finished as highly polished 'showroom chrome' as if it were a completed frame and I guess it was intended to be a display piece rather than for use. I'm looking for a company that can weld these finished pieces together and complete the frame - is this possible? and would the bike need to be re-finished afterwards? The bike has the decals in place. I have a replica frame that is welded so dimensions wouldn't be an issue
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